Iron, inflammation, and early death in adults with sickle cell disease

Endurance training and hydroxyurea have synergistic effects on muscle function and energetics in sickle cell disease mice

Sickle cell disease (SCD) is an hemoglobinopathy resulting in the production of an abnormal Hb (HbS) which can polymerize in deoxygenated conditions, leading to the sickling of red blood cells (RBC). These alterations can decrease the oxygen-carrying capacity leading to impaired function and energetics of skeletal muscle. Any strategy which could reverse the corresponding defects could be of interest. In SCD, endurance training is known to improve multiples muscle properties which restores patient's exercise capacity but present reduced effects in anemic patients. Hydroxyurea (HU) can increase fetal hemoglobin production which can reduce anemia in patients. The present study was conducted to determine whether HU can improve the effects of endurance training to improve muscle function and energetics. Twenty SCD Townes mice have been trained for 8 weeks with (n = 11) or without (n = 9) HU. SCD mice muscle function and energetics were analyzed during a standardized rest-exercise-recovery protocol, using Phosphorus-31 Magnetic resonance spectroscopy (31P-MRS) and transcutaneous stimulation. The combination of training and HU specifically decreased fatigue index and PCr consumption while muscle oxidative capacity was improved. These results illustrate the potential synergistic effects of endurance training and HU on muscle function and energetics in sickle cell disease.

Ferroptosis as an emerging target in sickle cell disease

Sickle cell disease (SCD) is an inherited hemoglobin disorder marked by red blood cell sickling, resulting in severe anemia, painful episodes, extensive organ damage, and shortened life expectancy. In SCD, increased iron levels can trigger ferroptosis, a specific type of cell death characterized by reactive oxygen species (ROS) and lipid peroxide accumulation, leading to damage and organ impairments. The intricate interplay between iron, ferroptosis, inflammation, and oxidative stress in SCD underscores the necessity of thoroughly understanding these processes for the development of innovative therapeutic strategies. This review highlights the importance of balancing the complex interactions among various factors and exploitation of the knowledge in developing novel therapeutics for this devastating disease.

Transcriptome profiling reveals distinct alterations in the B-cell signature and dysregulation of peripheral B-cell subsets in sickle cell anemia patients

Sickle cell anemia (SCA) is characterized by immune system activation and heightened susceptibility to infections. We hypothesized that SCA patients exhibit transcriptional alterations in B-cell-related genes, impacting their peripheral B-cell compartment and leading to dysregulated humoral immunity and increased infection susceptibility. Our objective was to conduct an in silico analysis of whole blood transcriptomes from SCA patients and healthy controls obtained from public repositories. We aimed to identify alterations in the adaptive immune system and validate these findings in our own SCA patient cohort. Bioinformatic analyses unveiled significant transcriptional alterations in B-cell signatures, developmental pathways, and signaling pathways. These results were validated in peripheral blood mononuclear cells from our SCA patient cohort and controls using real-time polymerase chain reaction and flow cytometry. Ninety genes exhibited differential expression, with 70 upregulated and 20 downregulated. Dysregulation in the B-cell compartment of SCA patients was evident, characterized by increased frequencies of immature and naive B-cells, and decreased percentages of memory B-cell subsets compared with healthy controls. Our findings highlight previously unexplored transcriptional and quantitative alterations in peripheral B-cells among SCA patients. Understanding these changes sheds light on the mechanisms contributing to the heightened infection risk in this population. Future studies should delve deeper into these molecular changes to develop targeted interventions and therapeutic strategies aimed at mitigating infection susceptibility in individuals with SCA.

Neutrophils in sickle cell disease: Exploring their potential role as a therapeutic target

Factors influencing the activation of neutrophils in SCD and the potential neutrophil-mediated ameliorating effects of therapies in SCD.

An 8-Week study on the effects of high and Moderate-Intensity interval exercises on mitochondrial MOTS-C changes and their relation to metabolic markers in male diabetic sand rats

Mitochondrial dysfunction is a significant feature of type 2 diabetes. MOTS-C, a peptide derived from mitochondria, has positive effects on metabolism and exercise capacity. This study explored the impact of high and moderate-intensity interval exercises on mitochondrial MOTS-C alterations and their correlation with metabolic markers in male diabetic sand rats. Thirty male sand rats were divided into six groups: control, MIIT, DM + HIIT, DM + MIIT, DM, and HIIT (5 rats each). Diabetes was induced using a high-fat diet (HFD) combined with streptozotocin (STZ). The Wistar sand rats in exercise groups underwent 8 weeks of interval training of varying intensities. Post sample collection, protein expressions of PCG-1a, AMPK, and GLUT4 were assessed through Western blot analysis, while MOTS-C protein expression was determined using ELISA. Both exercise intensity and diabetes significantly affected the levels of PCG-1a, MOTS-C, GLUT4 proteins, and insulin resistance (p < 0.001). The combined effect of diabetes status and exercise intensity on these levels was also significant (p < 0.001). However, the diabetes effect varied when comparing high-intensity to moderate-intensity exercise. The moderate-intensity exercise group with diabetes showed higher levels of PCG-1a, MOTS-C, and GLUT4 proteins and reduced insulin resistance levels (p < 0.001). Exercise intensity (p = 0.022) and diabetes (p = 0.008) significantly influenced AMPK protein levels. The interplay between diabetes status and exercise intensity on AMPK protein levels was noteworthy, with the moderate-intensity diabetes group exhibiting higher AMPK levels than the high-intensity diabetes group (p < 0.001). In conclusion, exercise elevates the levels of PCG-1a, MOTS-C, GLUT4, and AMPK proteins, regulating insulin resistance in diabetic sand rats. Given the AMPK-MOTS-C mitochondrial pathway's mechanisms, interval exercises might enhance the metabolic rates and general health of diabetic rodents.

Potential inflammatory targets in the integrative health care of patients with sickle cell disease

Inflammation plays an integral role in the complications of sickle cell disease (SCD), which can lead to vaso-occlusive crisis and extreme pain. SCD is accompanied by numerous complications, including cardiovascular disease, cognitive decline and endothelial dysfunction, contributing to mortality. As disease severity increases with age, the present study aimed to assess if age is also correlated with a definite pattern of progression of the two inflammatory markers, high-sensitivity C-reactive protein (hsCRP) and total homocysteine (tHCY). The findings of the present study could lead to an improved understanding of the threshold levels of these inflammatory markers and timely interventions to delay complications. In an observational study, levels of hsCRP and tHCY were analyzed in 70 patients (35 male and 35 female patients) with SCD aged between 5 and 16 years. hsCRP levels were in the high-risk range in 64.29% (n=45) of all male and female patients. A sex-wise distribution showed that, of the 35 male patients, 74.28% (n=26) were in the high-risk range, and of the 35 female patients, 54.28% (n=19) were in the high-risk range. An age-wise distribution showed that of the 41 patients in the 5-10-years age group, 70.73% (n=29), were in the high-risk range. In comparison, of the 29 patients in the 11-16-years age group, 55.17% (n=16) were in the high-risk range. tHCY levels were observed to be in the normal range in 98.57% (n=69) of all children, as compared with 1.43% (n=1) in the high-risk range. Furthermore, a sex-wise distribution showed that female patients in the high-risk group of hsCRP had higher concentrations of tHCY as compared with the male patients in that risk group. An age-wise distribution of hsCRP concentration also showed that the risk of CVD in patients in the 11-16-years age group was higher with increased concentrations of tHCY. A weak negative correlation was observed between age and hsCRP concentrations (r-value=-0.280; P=0.026) and a weak positive correlation was detected between tHCY and age (r-value=0.259; P=0.036). In conclusion, the results of the present study indicated that higher levels of hsCRP could be a useful marker in children with SCD, and levels of tHCY may be an adjunct marker as the disease progresses with age.

An open-label, multicenter, phase 2 study of a food enriched with docosahexaenoic acid in adults with sickle cell disease

Sickle cell disease (SCD) induces red blood cell sickling, which causes debilitating symptoms including vaso-occlusion and inflammation. We investigated a food enriched with omega-3 fatty acids to determine its effect on certain factors: blood cell membrane fatty acid composition (including anti-inflammatory elements-docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)-and the pro-inflammatory, arachidonic acid (AA)); the inflammation biomarker, C-reactive protein (CRP); and vaso-occlusive crisis (VOC) pain. Ten adults with SCD ingested the food, daily, for 28 days. Evaluated measures included blood cell membrane fatty acid ratios (AA vs omega-3 (DHA+EPA)), CRP (mg/L) levels, and Visual Analogue Scale (VAS) scores (a VOC assessment). The food was well tolerated and led to a statistically significant CRP reduction (39%). However, changes in omega-3 fatty acid ratios and VAS scores were not significant. Overall, while the omega-3-enriched food reduced inflammation, larger, blinded studies are needed to assess its effectiveness on other measures.

Variation and impact of polygenic hematologic traits in monogenic sickle cell disease

Several of the complications observed in sickle cell disease (SCD) are influenced by variation in hematologic traits (HT), such as fetal hemoglobin (HbF) level and neutrophil count. Previous large-scale genome-wide association studies carried out in largely healthy individuals have identified thousands of variants associated with HT, which have then been used to develop multi-ancestry polygenic trait scores (PTS). Here, we tested whether these PTS associate with HT in SCD patients and if they can improve statistical models associated with SCD-related complications. In 2,056 SCD patients, we found that the PTS predicted less HT variance than in non-SCD individuals of African ancestry. This was particularly striking at the Duffy/DARC locus, where we observed an epistatic interaction between the SCD genotype and the Duffy null variant (rs2814778) that led to a two-fold weaker effect on neutrophil count. PTS for these HT which are measured as part of routine practice were not associated with complications in SCD. In contrast, we found that a simple PTS for HbF that includes only six variants explained a large fraction of the phenotypic variation (20.5-27.1%), associated with acute chest syndrome and stroke risk, and improved the statistical modeling of the vaso-occlusive crisis rate. Using Mendelian randomization, we found that increasing HbF by 4.8% reduces stroke risk by 39% (P=0.0006). Taken together, our results highlight the importance of validating PTS in large diseased populations before proposing their implementation in the context of precision medicine initiatives.

NLRP3 inflammasome activation in response to metals

Implant surgery is followed by a series of inflammatory reactions that directly affect its postoperative results. The inflammasome plays a vital role in the inflammatory response by inducing pyroptosis and producing interleukin-1β, which plays a critical role in inflammation and tissue damage. Therefore, it is essential to study the activation of the inflammasome in the bone healing process after implant surgery. As metals are the primary implant materials, metal-induced local inflammatory reactions have received significant attention, and there has been more and more research on the activation of the NLRP3 (NOD-like receptor protein-3) inflammasome caused by these metals. In this review, we consolidate the basic knowledge on the NLRP3 inflammasome structures, the present knowledge on the mechanisms of NLRP3 inflammasome activation, and the studies of metal-induced NLRP3 inflammasome activation.

The NLRP3 inflammasome fires up heme-induced inflammation in hemolytic conditions

Overactive inflammatory responses are central to the pathophysiology of many hemolytic conditions including sickle cell disease. Excessive hemolysis leads to elevated serum levels of heme due to saturation of heme scavenging mechanisms. Extracellular heme has been shown to activate the NLRP3 inflammasome, leading to activation of caspase-1 and release of pro-inflammatory cytokines IL-1β and IL-18. Heme also activates the non-canonical inflammasome pathway, which may contribute to NLRP3 inflammasome formation and leads to pyroptosis, a type of inflammatory cell death. Some clinical studies indicate there is a benefit to blocking the NLRP3 inflammasome pathway in patients with sickle cell disease and other hemolytic conditions. However, a thorough understanding of the mechanisms of heme-induced inflammasome activation is needed to fully leverage this pathway for clinical benefit. This review will explore the mechanisms of heme-induced NLRP3 inflammasome activation and the role of this pathway in hemolytic conditions including sickle cell disease.

Dietary iron restriction protects against vaso-occlusion and organ damage in murine sickle cell disease

Sickle cell disease (SCD) is an inherited disorder resulting from a β-globin gene mutation, and SCD patients experience erythrocyte sickling, vaso-occlusive episodes (VOE), and progressive organ damage. Chronic hemolysis, inflammation, and repeated red blood cell transfusions in SCD can disrupt iron homeostasis. Patients who receive multiple blood transfusions develop iron overload, and another subpopulation of SCD patients manifest iron deficiency. To elucidate connections between dietary iron, the microbiome, and SCD pathogenesis, we treated SCD mice with an iron-restricted diet (IRD). IRD treatment reduced iron availability and hemolysis, decreased acute VOE, and ameliorated chronic organ damage in SCD mice. Our results extend previous studies indicating that the gut microbiota regulate disease in SCD mice. IRD alters microbiota load and improves gut integrity, together preventing crosstalk between the gut microbiome and inflammatory factors such as aged neutrophils, dampening VOE, and organ damage. These findings provide strong evidence for the therapeutic potential of manipulating iron homeostasis and the gut microbiome to ameliorate SCD pathophysiology. Many treatments, which are under development, focus on lowering the systemic iron concentration to relieve disease complications, and our data suggest that iron-induced changes in microbiota load and gut integrity are related- and novel-therapeutic targets.

Managing the Cerebrovascular Complications of Sickle Cell Disease: Current Perspectives

The importance of protecting brain function for people with sickle cell disease (SCD) cannot be overstated. SCD is associated with multiple cerebrovascular complications that threaten neurocognitive function and life. Without screening and preventive management, 11% of children at 24% of adults with SCD have ischemic or hemorrhagic strokes. Stroke screening in children with SCD is well-established using transcranial Doppler ultrasound (TCD). TCD velocities above 200 cm/s significantly increase the risk of stroke, which can be prevented using chronic red blood cell (RBC) transfusion. RBC transfusion is also the cornerstone of acute stroke management and secondary stroke prevention. Chronic transfusion requires long-term management of complications like iron overload. Hydroxyurea can replace chronic transfusions for primary stroke prevention in a select group of patients or in populations where chronic transfusions are not feasible. Silent cerebral infarction (SCI) is even more common than stroke, affecting 39% of children and more than 50% of adults with SCD; management of SCI is individualized and includes careful neurocognitive evaluation. Hematopoietic stem cell transplant prevents cerebrovascular complications, despite the short- and long-term risks. Newer disease-modifying agents like voxelotor and crizanlizumab, as well as gene therapy, may treat cerebrovascular complications, but these approaches are investigational.

Flurbiprofen inhibits heme induced NLRP3 inflammasome in Berkeley sickle cell disease mice

Sickle cell disease (SCD) is accompanied by several complications, which emanate from the sickling of erythrocytes due to a point mutation in the β-globin chain of hemoglobin. Sickled erythrocytes are unable to move smoothly through small blood capillaries and therefore, cause vaso occlusion and severe pain. Apart from pain, continuous lysis of fragile sickled erythrocytes leads to the release of heme, which is a strong activator of the NLRP3 inflammasome, thus producing chronic inflammation in sickle cell disease. In this study, we identified flurbiprofen among other COX-2 inhibitors to be a potent inhibitor of heme-induced NLRP3 inflammasome. We found that apart from being a nociceptive agent, flurbiprofen exerts a strong anti-inflammatory effect by suppressing NF-κB signaling, which was evidenced by reduced levels of TNF-α and IL-6 in wild-type and sickle cell disease Berkeley mice models. Our data further demonstrated the protective effect of flurbiprofen on liver, lungs, and spleen in Berkeley mice. The current sickle cell disease pain management regime relies mainly on opiate drugs, which is accompanied by several side effects without modifying the sickle cell disease-related pathology. Considering the potent role of flurbiprofen in inhibiting NLRP3 inflammasome and other inflammatory cytokines in sickle cell disease, our data suggests that it can be explored further for better sickle cell disease pain management along with the possibility of disease modification.

HbS promotes TLR4-mediated monocyte activation and proinflammatory cytokine production in sickle cell disease

Monocytes are considered crucial actors of inflammation in sickle cell disease (SCD), being responsible for an increased production of proinflammatory cytokines such as tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), and IL-6. Although a role of free heme released by intravascular hemolysis has been suspected, the mechanisms underlying monocyte activation in patients with SCD remain unknown. Using purified human hemoglobin (Hb), we demonstrate herein, that cell-free HbS, unlike HbA or heme, is responsible for a major enhancement in the expression of proinflammatory cytokines by human monocytes. This effect was found mediated by direct interaction with the Toll-like receptor 4 (TLR4)/myeloid differentiation factor 2 (MD-2) complex, resulting in the activation of both the nuclear factor-κB (NF-κB) and type I interferon pathways. In Townes SCD mice, injection of HbS, unlike HbA, was responsible for an increased production of proinflammatory cytokines, which was prevented by the TLR4 inhibitor, TAK-242. Our results reveal a novel mechanism of monocyte activation and systemic inflammation in SCD, which opens new promising therapeutic perspectives targeting the HbS-TLR4 interaction.

Deferiprone for transfusional iron overload in sickle cell disease and other anemias: open-label study of up to 3 years

Long-term safety and efficacy data on the iron chelator deferiprone in sickle cell disease (SCD) and other anemias are limited. FIRST-EXT was a 2-year extension study of FIRST (Ferriprox in Patients With Iron Overload in Sickle Cell Disease Trial), a 1-year, randomized noninferiority study of deferiprone vs deferoxamine in these populations. Patients who entered FIRST-EXT continued to receive, or were switched to, deferiprone. Altogether, 134 patients were enrolled in FIRST-EXT (mean age: 16.2 years), with mean (SD) exposure to deferiprone of 2.1 (0.8) years over the 2 studies. The primary end point was safety. Secondary end points were change in liver iron concentration (LIC), cardiac T2∗, serum ferritin (SF), and the proportion of responders (≥20% improvement in efficacy measure). The most common adverse events considered at least possibly related to deferiprone were neutropenia (9.0%) and abdominal pain (7.5%). LIC (mg/g dry weight) decreased over time, with mean (SD) changes from baseline at each time point (year 1, -2.64 [4.64]; year 2, -3.91 [6.38]; year 3, -6.64 [7.72], all P < .0001). Mean SF levels (μg/L) decreased significantly after year 2 (-771, P = .0008) and year 3 (-1016, P = .0420). Responder rates for LIC and SF increased each year (LIC: year 1, 46.5%; year 2, 57.1%; year 3, 66.1%; SF: year 1, 35.2%; year 2, 55.2%; year 3, 70.9%). Cardiac T2∗ remained normal in all patients. In conclusion, long-term therapy with deferiprone was not associated with new safety concerns and led to continued and progressive reduction in iron load in individuals with SCD or other anemias. The trial was registered at www.clinicaltrials.gov as #NCT02443545.

Immunomodulatory actions of a kynurenine-derived endogenous electrophile

The up-regulation of kynurenine metabolism induces immunomodulatory responses via incompletely understood mechanisms. We report that increases in cellular and systemic kynurenine levels yield the electrophilic derivative kynurenine-carboxyketoalkene (Kyn-CKA), as evidenced by the accumulation of thiol conjugates and saturated metabolites. Kyn-CKA induces NFE2 like bZIP transcription factor 2- and aryl hydrocarbon receptor-regulated genes and inhibits nuclear factor κB- and NLR family pyrin domain containing 3-dependent proinflammatory signaling. Sickle cell disease (SCD) is a hereditary hemolytic condition characterized by basal inflammation and recurrent vaso-occlusive crises. Both transgenic SCD mice and patients with SCD exhibit increased kynurenine and Kyn-CKA metabolite levels. Plasma hemin and kynurenine concentrations are positively correlated, indicating that Kyn-CKA synthesis in SCD is up-regulated during pathogenic vascular stress. Administration of Kyn-CKA abrogated pulmonary microvasculature occlusion in SCD mice, an important factor in lung injury development. These findings demonstrate that the up-regulation of kynurenine synthesis and its metabolism to Kyn-CKA is an adaptive response that attenuates inflammation and protects tissues.

Molecular Mechanisms of Hepatic Dysfunction in Sickle Cell Disease: Lessons From The Townes Mouse Model

Sickle cell disease (SCD) is an autosomal-recessive-genetic disorder that affects ~100,000 Americans and millions of people worldwide. Erythrocyte sickling, vaso-occlusion, sterile inflammation and hemolysis are the major pathophysiological pathways leading to liver injury in SCD. Although hepatic dysfunction affects up to 10-40% of SCD patients, therapeutic approaches to prevent liver injury in SCD are not known, and the molecular mechanisms promoting progressive liver injury in SCD remain poorly understood. Animal models have been beneficial in bridging the gap between preclinical and translational research in SCD. Recent advances in methodology have allowed the development of several humanized mouse models to address various aspects of SCD related liver diseases. This review provides an overview of current knowledge of the molecular mechanisms and potential therapeutic options of SCD associated liver dysfunction using the Townes mouse model.

Role of Serum Ferritin in Predicting Outcomes of COVID-19 Infection Among Sickle Cell Disease Patients: A Systematic Review and Meta-Analysis

Patients with sickle cell disease (SCD) are at higher risk of getting severe COVID-19 infection. This systematic review and meta-analysis aimed to determine the role of serum ferritin in predicting ICU admission and mortality among patients with SCD following COVID-19 infection. A systematic search was conducted in PubMed, Scopus, Web of Science, Embase, WHO COVID-19 database, ProQuest, and Cochrane Library for articles published between 1st December 2019 to 31st November 2021. Methodological quality was assessed using the Joanna Briggs Institute (JBI) critical appraisal checklists. Eleven articles (7 cohorts and 4 case series) were included in this review. Pooled mean serum ferritin level on admission was 1581.62 ng/mL while pooled proportion of ICU admission and mortality were 0.10 (95% CI 0.06; 0.16, prediction interval 0.04; 0.23, p = 0.29, I² = 17%) and 0.07 (95% CI 0.05; 0.11, prediction interval 0.04; 0.12, p = 0.68, I² = 0%) respectively. Meta-regression showed that serum ferritin did not predict for both ICU admission (regression coefficient = 0.0001, p = 0.3523) and mortality (regression coefficient = 0.0001, p = 0.4029). Our analyses showed that serum ferritin may not be a useful marker to predict the outcomes of COVID-19 infection among patients with SCD. More data are required to identify a reliable tool to identify patients with SCD who are at risk of getting severe COVID-19 infection.

HIV-1 infection in sickle cell disease and sickle cell trait: role of iron and innate response

INTRODUCTION

Sickle cell disease (SCD), an inherited hemoglobinopathy, affects primarily African Americans in the U.S.A. In addition, about 15% African Americans carry sickle cell trait (SCT). Despite the risk associated with blood transfusions, SCD patients have lower risk of acquiring HIV-1 infection. SCT individuals might also have some protection from HIV-1 infection.

AREAS COVERED

Here, we will review recent and previous studies with the focus on molecular mechanisms that might underlie and contribute to the protection of individuals with SCD and SCT from HIV-1 infection. As both of these conditions predispose to hemolysis, we will focus our discussion on the effects of systemic and intracellular iron on HIV-1 infection and progression. We will also review changes in iron metabolism and activation of innate antiviral responses in SCD and SCT and their effects on HIV-1 infection.

EXPERT OPINION

Previous studies, including ours, showed that SCD might protect from HIV-1 infection. This protection is likely due to the upregulation of complex protein network in response to hemolysis, hypoxia and interferon signaling. These findings are important not only for HIV-1 field but also for SCD cure efforts as antiviral state of SCD patients may adversely affect lentivirus-based gene therapy efforts.

A randomized, placebo-controlled, double-blind trial of canakinumab in children and young adults with sickle cell anemia

Excessive intravascular release of lysed cellular contents from damaged red blood cells (RBCs) in patients with sickle cell anemia (SCA) can activate the inflammasome, a multiprotein oligomer promoting maturation and secretion of pro-inflammatory cytokines, including interleukin 1-beta (IL-1b). We hypothesized that IL-1b blockade by canakinumab in patients with SCA would reduce markers of inflammation and clinical disease activity. In this randomized, double-blind, multi-center phase 2a study, patients aged 8-20 years old with SCA (HbSS or HbSb0thalassemia), history of acute pain episodes and elevated hsCRP >1.0 mg/L at screening were randomized 1:1 to received 6 monthly treatments with 300 mg s.c. canakinumab or placebo. Measured outcomes at baseline and weeks 4, 8, 12, 16, 20 and 24 included electronic patient-reported outcomes, hospitalization rate and adverse events (AEs) and serious AEs (SAEs). All but one of the 49 enrolled patients were receiving stable background hydroxyurea therapy. Although the primary objective (pre-specified reduction of pain) was not met, compared to placebo-arm patients, canakinumab-treated patients had reductions in markers of inflammation, occurrence of SCA-related AE and SAE, and number and duration of hospitalizations, as well as trends for improvement in pain intensity, fatigue and absences from school or work. Post-hoc analysis revealed treatment effects on weight, restricted to pediatric patients. Canakinumab was well tolerated with no treatment-related SAEs and no new safety signal. These findings demonstrate that the inflammation associated with SCA can be reduced by selective IL-1b blockade by canakinumab with potential for therapeutic benefits. This trial was registered at www.clinicaltrials.gov as NCT02961218.

The Role of RBC Oxidative Stress in Sickle Cell Disease: From the Molecular Basis to Pathologic Implications

Sickle cell disease (SCD) is an inherited monogenic disorder and the most common severe hemoglobinopathy in the world. SCD is characterized by a point mutation in the β-globin gene, which results in hemoglobin (Hb) S production, leading to a variety of mechanistic and phenotypic changes within the sickle red blood cell (RBC). In SCD, the sickle RBCs are the root cause of the disease and they are a primary source of oxidative stress since sickle RBC redox state is compromised due to an imbalance between prooxidants and antioxidants. This imbalance in redox state is a result of a continuous production of reactive oxygen species (ROS) within the sickle RBC caused by the constant endogenous Hb autoxidation and NADPH oxidase activation, as well as by a deficiency in the antioxidant defense system. Accumulation of non-neutralized ROS within the sickle RBCs affects RBC membrane structure and function, leading to membrane integrity deficiency, low deformability, phosphatidylserine exposure, and release of micro-vesicles. These oxidative stress-associated RBC phenotypic modifications consequently evoke a myriad of physiological changes involved in multi-system manifestations. Thus, RBC oxidative stress in SCD can ultimately instigate major processes involved in organ damage. The critical role of the sickle RBC ROS production and its regulation in SCD pathophysiology are discussed here.

Point-of-care microchip electrophoresis for integrated anemia and hemoglobin variant testing

Anemia affects over 25% of the world's population with the heaviest burden borne by women and children. Genetic hemoglobin (Hb) variants, such as sickle cell disease, are among the major causes of anemia. Anemia and Hb variant are pathologically interrelated and have an overlapping geographical distribution. We present the first point-of-care (POC) platform to perform both anemia detection and Hb variant identification, using a single paper-based electrophoresis test. Feasibility of this new integrated diagnostic approach is demonstrated via testing individuals with anemia and/or sickle cell disease. Hemoglobin level determination is performed by an artificial neural network (ANN) based machine learning algorithm, which achieves a mean absolute error of 0.55 g dL^-1 and a bias of -0.10 g dL^-1 against the gold standard (95% limits of agreement: 1.5 g dL^-1) from Bland-Altman analysis on the test set. Resultant anemia detection is achieved with 100% sensitivity and 92.3% specificity. With the same tests, subjects with sickle cell disease were identified with 100% sensitivity and specificity. Overall, the presented platform enabled, for the first time, integrated anemia detection and hemoglobin variant identification using a single point-of-care test.

Genetic contribution and functional impairment of inflammasome in sickle cell disease

BACKGROUND

Sickle cell disease (SCD), one of the most common single-gene disorders, is caused by mutations in the hemoglobin ß-chain gene. Clinical presentation is heterogeneous, and inflammation is a common condition. Thereby, we hypothesized that inflammasome and related cytokine IL-1ß could represent significant SCD pathogenesis contributors.

MATERIAL AND METHODS

161 SCD (SS/Sβ) patients were enrolled for the study. Seven single nucleotide polymorphisms (SNPs) in 5 inflammasome genes (NLRP1, NLRP3, NLRC4, CARD8, IL1B) were selected based on minor allele frequency. Total peripheral blood mononuclear cells (PBMC) and monocytes were isolated from 10 out of 161 SCD patients (HbSS) and 10 healthy donors (control group, Ctrl) for inflammasome analysis.

RESULTS

SCD patients presented a functional impairment of inflammasome, with monocytes and peripheral blood mononuclear cells (PBMC) exhibiting a different NLRP3 inflammasome activation rate. Gain-of-function variants in NLRP1 and IL1B genes resulted associated with a mild SCD clinical presentation.

DISCUSSION

Our results can contribute to the understanding of SCD inflammation. SCD patients showed possible exhaustion of monocytes due to chronic inflammation, moreover others cells in PBMC can contribute to the NLRP3 inflammasome activation. NLRP1 gain-of-function was associated with mild clinical presentation, suggesting that other inflammasome receptors can be involved in SCD. This is the first study reporting a significant contribution of inflammasome SNPs in SCD.

Noncanonical Roles of Caspase-4 and Caspase-5 in Heme-Driven IL-1β Release and Cell Death

Excessive release of heme from RBCs is a key pathophysiological feature of several disease states, including bacterial sepsis, malaria, and sickle cell disease. This hemolysis results in an increased level of free heme that has been implicated in the inflammatory activation of monocytes, macrophages, and the endothelium. In this study, we show that extracellular heme engages the human inflammatory caspases, caspase-1, caspase-4, and caspase-5, resulting in the release of IL-1β. Heme-induced IL-1β release was further increased in macrophages from patients with sickle cell disease. In human primary macrophages, heme activated caspase-1 in an inflammasome-dependent manner, but heme-induced activation of caspase-4 and caspase-5 was independent of canonical inflammasomes. Furthermore, we show that both caspase-4 and caspase-5 are essential for heme-induced IL-1β release, whereas caspase-4 is the primary contributor to heme-induced cell death. Together, we have identified that extracellular heme is a damage-associated molecular pattern that can engage canonical and noncanonical inflammasome activation as a key mediator of inflammation in macrophages.

Immunological Hallmarks of Inflammatory Status in Vaso-Occlusive Crisis of Sickle Cell Anemia Patients

Sickle Cell Anemia (SCA) is the most common genetic disorder around the world. The mutation in the β-globin gene is responsible for a higher hemolysis rate, with further involvement of immunological molecules, especially cytokines, chemokines, growth factors, and anaphylatoxins. These molecules are responsible for inducing and attracting immune cells into circulation, thus contributing to increases in leukocytes and other pro-inflammatory mediators, and can culminate in a vaso-occlusive crisis (VOC). This study aimed to characterize the levels of these molecules in SCA patients in different clinical conditions in order to identify potential hallmarks of inflammation in these patients. An analytical prospective study was conducted using the serum of SCA patients in steady-state (StSt; n = 27) and VOC (n = 22), along with 53 healthy donors (HD). Samples from the VOC group were obtained on admission and on discharge, in the convalescent phase (CV). Levels of chemokines (CXCL8, CXCL10, CL2, CLL3, CCL4, CL5, and CCL11), cytokines (IL-1β, IL-1ra, IL-2, IL-4, IL-5, IL-6, IL-7, IL-10, IL-12p70, IL-13, IL-17A, TNF-α, and IFN-γ) and growth factors (VEGF, FGFb, PDGF-BB, GM-CSF, and G-CSF) were measured using a Luminex assay, and anaphylatoxins (C3a, C4a, and C5a) were measured using Cytometric Bead Array. SCA patients in StSt showed a pro-inflammatory profile, and were indicated as being higher producers of CCL2, IL-1β, IL-12p70, IFN-γ, IL-17A, and GM-CSF, while VOC is highlighted by molecules IL-4 and IL-5, but also IL-2, IL-7, PDGF-BB, and G-CSF. PDGF-BB and IL-1ra seemed to be two important hallmarks for the acute-to-chronic stage, due to their significant decrease after crisis inflammation and statistical difference in VOC and CV groups. These molecules show higher levels and a strong correlation with other molecules in VOC. Furthermore, they remain at higher levels even after crisis recovery, which suggest their importance in the role of inflammation during crisis and participation in immune cell adhesion and activation. These results support a relevant role of cytokines, neutrophil and monocytes, since these may act as markers of VOC inflammation in SCA patients.

Sickle Cell Disease: Role of Oxidative Stress and Antioxidant Therapy

Sickle cell disease (SCD) is the most common hereditary disorder of hemoglobin (Hb), which affects approximately a million people worldwide. It is characterized by a single nucleotide substitution in the β-globin gene, leading to the production of abnormal sickle hemoglobin (HbS) with multi-system consequences. HbS polymerization is the primary event in SCD. Repeated polymerization and depolymerization of Hb causes oxidative stress that plays a key role in the pathophysiology of hemolysis, vessel occlusion and the following organ damage in sickle cell patients. For this reason, reactive oxidizing species and the (end)-products of their oxidative reactions have been proposed as markers of both tissue pro-oxidant status and disease severity. Although more studies are needed to clarify their role, antioxidant agents have been shown to be effective in reducing pathological consequences of the disease by preventing oxidative damage in SCD, i.e., by decreasing the oxidant formation or repairing the induced damage. An improved understanding of oxidative stress will lead to targeted antioxidant therapies that should prevent or delay the development of organ complications in this patient population.

Heme Causes Pain in Sickle Mice via Toll-Like Receptor 4-Mediated Reactive Oxygen Species- and Endoplasmic Reticulum Stress-Induced Glial Activation

Aims: Lifelong pain is a hallmark feature of sickle cell disease (SCD). How sickle pathobiology evokes pain remains unknown. We hypothesize that increased cell-free heme due to ongoing hemolysis activates toll-like receptor 4 (TLR4), leading to the formation of reactive oxygen species (ROS) and endoplasmic reticulum (ER) stress. Together, these processes lead to spinal microglial activation and neuroinflammation, culminating in acute and chronic pain. Results: Spinal heme levels, TLR4 transcripts, oxidative stress, and ER stress were significantly higher in sickle mice than controls. In vitro, TLR4 inhibition in spinal cord microglial cells attenuated heme-induced ROS and ER stress. Heme treatment led to a time-dependent increase in the characteristic features of sickle pain (mechanical and thermal hyperalgesia) in both sickle and control mice; this effect was absent in TLR4-knockout sickle and control mice. TLR4 deletion in sickle mice attenuated chronic and hypoxia/reoxygenation (H/R)-evoked acute hyperalgesia. Sickle mice treated with the TLR4 inhibitor resatorvid; selective small-molecule inhibitor of TLR4 (TAK242) had significantly reduced chronic hyperalgesia and had less severe H/R-evoked acute pain with quicker recovery. Notably, reducing ER stress with salubrinal ameliorated chronic hyperalgesia in sickle mice. Innovation: Our findings demonstrate the causal role of free heme in the genesis of acute and chronic sickle pain and suggest that TLR4 and/or ER stress are novel therapeutic targets for treating pain in SCD. Conclusion: Heme-induced microglial activation via TLR4 in the central nervous system contributes to the initiation and maintenance of sickle pain via ER stress in SCD. Antioxid. Redox Signal. 34, 279-293.

The multifaceted role of ischemia/reperfusion in sickle cell anemia

Sickle cell anemia is a unique disease dominated by hemolytic anemia and vaso-occlusive events. The latter trigger a version of ischemia/reperfusion (I/R) pathobiology that is singular in its origin, cyclicity, complexity, instability, perpetuity, and breadth of clinical consequences. Specific clinical features are probably attributable to local I/R injury (e.g., stroke syndromes) or remote organ injury (e.g., acute chest syndrome) or the systematization of inflammation (e.g., multifocal arteriopathy). Indeed, by fashioning an underlying template of endothelial dysfunction and vulnerability, the robust inflammatory systematization no doubt contributes to all sickle pathology. In this Review, we highlight I/R-targeting therapeutics shown to improve microvascular blood flow in sickle transgenic mice undergoing I/R, and we suggest how such insights might be translated into human therapeutic strategies.

An evaluation of ticagrelor for the treatment of sickle cell anemia

INTRODUCTION

Ticagrelor is an antiplatelet agent approved for the treatment of patients with an acute coronary syndrome or a history of myocardial infarction. Considering the evidence demonstrating that ticagrelor-mediated inhibition of platelet activation and aggregation have beneficial effects in the treatment of thrombotic conditions, clinical studies have been conducted to evaluate the use of this drug for the treatment of sickle cell disease (SCD), demonstrating satisfactory tolerability and safety.

AREAS COVERED

Clinical investigation has characterized the pharmacokinetic and pharmacodynamical profile, as well as the efficacy and safety of ticagrelor to prevent painful vaso-occlusive crisis (painful episodes and acute chest syndrome) in SCD patients.

EXPERT OPINION

While phase 1 and 2 clinical trials demonstrated satisfactory tolerability and safety, the conclusion of phase 3 clinical trials is crucial to prove the efficacy of ticagrelor as a therapeutic option for the treatment of SCD. Thus, it is expected that ticagrelor, especially in combination with other drugs, will improve the clinical profile and quality of life of patients with SCD.

Decoding the role of SOD2 in sickle cell disease

Sickle cell disease (SCD) is an inherited hemoglobinopathy caused by a single point mutation in the β-globin gene. As a consequence, deoxygenated hemoglobin polymerizes triggering red blood cell sickling and hemolysis, vaso-occlusion, and ischemia/reperfusion. Allied to these pathologies is the overproduction of reactive oxygen species driven by hemoglobin Fenton chemistry and peroxidase reactions as well as by secondary activation of vascular oxidases, including NAD(P)H oxidase and xanthine oxidase. In addition, hypoxia, produced by sickle red blood cell occlusion, disrupts mitochondrial metabolism and generates excess superoxide through electron leak from the mitochondrial respiratory chain. Superoxide dismutase 2 (SOD2) is a mitochondrial-specific antioxidant enzyme that dismutates superoxide to hydrogen peroxide, which is then converted to water by catalase and glutathione peroxidase. In SCD, the antioxidant defense system is significantly diminished through decreased expression and activity levels of antioxidant enzymes, including superoxide dismutase, catalase, and glutathione peroxidase. From a translational perspective, genetic variants including a missense variant in SOD2 (valine to alanine at position 16) are present in 45% of people with African ancestry and are associated with increased sickle complications. While it is known that there is an imbalance between oxidative species and antioxidant defenses in SCD, much more investigation is warranted. This review summarizes our current understanding of antioxidant defense systems in SCD, particularly focused on SOD2, and provides insight into challenges and opportunities as the field moves forward.

Serum albumin is independently associated with higher mortality in adult sickle cell patients: Results of three independent cohorts

Sickle cell disease (SCD) impacts liver and kidney function as well as skin integrity. These complications, as well as the hyperinflammatory state of SCD, could affect serum albumin. Serum albumin has key roles in antioxidant, anti-inflammatory and antithrombotic pathways and maintains vascular integrity. In SCD, these pathways modulate disease severity and clinical outcomes. We used three independent SCD adult cohorts to assess clinical predictors of serum albumin as well its association with mortality. In 2553 SCD adult participants, the frequency of low (<35 g/L) serum albumin was 5%. Older age and lower hemoglobin (P <0.001) were associated with lower serum albumin in all three cohorts. In age and hemoglobin adjusted analysis, higher liver enzymes (P <0.05) were associated with lower serum albumin. In two of the three cohorts, lower kidney function as measured by Glomerular Filtration Rate (P<0.001) was associated with lower serum albumin. Lower serum albumin predicted higher risk of tricuspid regurgitation velocity ≥ 2.5 m/s (OR = 1.1 per g/L, P ≤0.01). In all three cohorts, patients with low serum albumin had higher mortality (adjusted HR ≥2.9, P ≤0.003). This study confirms the role of serum albumin as a biomarker of disease severity and prognosis in patients with SCD. Albumin as a biomarker and possible mediator of SCD severity should be studied further.

High levels of proinflammatory cytokines IL-6 and IL-8 are associated with a poor clinical outcome in sickle cell anemia

Sickle cell anemia (SCA) pathophysiology is characterized by the activation of sickle red blood cells, reticulocytes, leukocytes, platelets, and endothelial cells, and with the expression of several inflammatory molecules. Therefore, it is conceivable that variations in levels of proinflammatory cytokines may act as a signaling of differential clinical course in SCA. Here, we evaluated the clinical impact of proinflammatory cytokines interleukin 1-β (IL-1β), interleukin 6 (IL-6), and interleukin 8 (IL-8) in 79 patients with SCA, followed in a single reference center from northeastern Brazil. The main clinical/laboratory data were obtained from patient interview and medical records. The proinflammatory markers IL-1β, IL-6, and IL-8 were evaluated by using commercially available enzyme-linked immunosorbent assay kits. According to levels of the proinflammatory markers, we observed that patients who had a higher frequency of VOC per year (P = 0.0236), acute chest syndrome (P = 0.01), leg ulcers (P = 0.0001), osteonecrosis (P = 0.0006), stroke (P = 0.0486), and priapism (P = 0.0347) had higher IL-6 levels compared with patients without these clinical complications. Furthermore, increased levels of IL-8 were found in patients who presented leg ulcers (P = 0.0184). No significant difference was found for IL-1β levels (P > 0.05). In summary, the present study emphasizes the role of inflammation in SCA pathophysiology, reveals an association of IL-8 levels and leg ulcer occurrence, and indicates that IL-6 levels can be used as a useful predictor for poor outcomes in SCA.

Sickle Cell Anemia Patients Display an Intricate Cellular and Serum Biomarker Network Highlighted by TCD4+CD69+ Lymphocytes, IL-17/MIP-1β, IL-12/VEGF, and IL-10/IP-10 Axis

BACKGROUND

Sickle cell anemia (SCA) is associated with a chronic proinflammatory state characterized by elevated leukocyte count, mortality from severe recurrent infections, and subsequent vasoocclusive complications with leukocyte adhesion to the endothelium and increased plasma levels of inflammatory cytokines. The immune system has a close connection with morbidity in SCA, but further studies are needed to uncover the involvement of innate and adaptive immunities in modulating the SCA physiopathology. We performed measurements of the frequency of innate and adaptive immunity cells, cytokines, chemokines, and growth factors and immunophenotyping of Toll-like receptor and adhesion molecule expression in the blood of SCA patients and healthy donors to evaluate the different profiles of these biomarkers, the relationship among them, and their correlation to laboratory records and death risk. Material and Methods. Immunophenotyping of cells, Toll-like receptors, and adhesion molecules were performed from peripheral blood samples of SCA patients and healthy donors by flow cytometry and cytokine/chemokine/growth factor measurement by the Luminex technique performed from the serum of the same subjects.

RESULTS

Cells of adaptive immunity such as IL-12, IL-17, and IL-10 cytokines; IL-8, IP-10, MIP-1α, MIP-1β, and RANTES chemokines; and VEGF, FGF-basic, and GM-CSF growth factors were higher in SCA patients than healthy donors regardless of any laboratorial and clinical condition. However, high death risk appears to have relevant biomarkers.

CONCLUSION

In the SCA pathophysiology at steady state, there is a broad immunological biomarker crosstalk highlighted by TCD4+CD69+ lymphocytes, IL-12 and IL-17 inflammatory and IL-10 regulatory cytokines, MIP-1α, MIP-1β, and IP-10 chemokines, and VEGF growth factor. High expression of TLR2 in monocytes and VLA-4 in TCD8+ lymphocytes and high levels of MIP-1β and RANTES appear to be relevant in high death risk conditions. The high reticulocytosis and high death risk conditions present common correlations, and there seems to be a balance by the Th2 profile.

Fatores de risco para mortalidade em pacientes com doença falciforme: uma revisão integrativa

RESUMO Objetivo Sumarizar fatores de risco e indicadores de mortalidade em pacientes com doença falciforme. Método Revisão integrativa em periódicos indexados nas bases de dados CINAHL, PubMed/MEDLINE, Science Direct/SCOPUS, SciELO e Web of Science. A questão norteadora foi elaborada por meio da estratégia Population, variable, outcome (PVO). A busca ocorreu no portal de periódicos da Coordenação de Aperfeiçoamento de Pessoal de Nível Superior entre outubro e novembro de 2018. Resultados Dos 19 artigos, 18 eram coorte e um ensaio clínico randomizado. A amostra foi constituída, em sua maioria, pelo sexo feminino e genótipo HbSS. Se repetiram mais a taxa de mortalidade cumulativa e a curva de mortalidade global. Sete estudos identificaram fatores de risco com associação estatisticamente significativa para morte. Os mais frequentes foram o baixo nível de hemoglobina, variáveis hepáticas (enzimas fosfatase alcalina e transaminase glutâmico oxalacética) e cardiovasculares (velocidade de regurgitação da válvula tricúspide ≥ 2,5m/s). Conclusão e implicações para a prática Indicadores de mortalidade constituem ferramentas de manejo de pacientes com doença falciforme e prevenção de riscos e complicações. Há necessidade de estudos sobre os fatores relacionados à mortalidade desses pacientes. A prevenção do óbito, certamente, promoverá uma melhoria na qualidade de vida e na sobrevida dessa população.

Free heme regulates placenta growth factor through NRF2-antioxidant response signaling

Free heme activates erythroblasts to express and secrete Placenta Growth Factor (PlGF), an angiogenic peptide of the VEGF family. High circulating levels of PlGF have been associated in experimental animals and in patients with sickle cell disease with echocardiographic markers of pulmonary hypertension, a life-limiting complication associated with more intense hemolysis. We now show that the mechanism of heme regulation of PlGF requires the contribution of the key antioxidant response regulator NRF2. Mimicking the effect of heme, the NRF2 agonist sulforaphane stimulates the PlGF transcript level nearly 30-fold in cultured human erythroblastoid cells. Heme and sulforaphane also induce transcripts for NRF2 itself, its partners MAFF and MAFG, and its competitor BACH1. Furthermore, heme induction of the PlGF transcript is significantly diminished by the NRF2 inhibitor brusatol and by siRNA knockdown of the NRF2 and/or MAFG transcription factors. Chromatin immunoprecipitation experiments show that heme induces NRF2 to bind directly to the PlGF promoter region. In complementary in vivo experiments, mice injected with heme show a significant increase in their plasma PlGF protein as early as 3 h after treatment. Our results reveal an important mechanism of PlGF regulation, adding to the growing literature that supports the pivotal importance of the NRF2 axis in the pathobiology of sickle cell disease.

Critical role of C5a in sickle cell disease

Innate immune complement activation may contribute to sickle cell disease (SCD) pathogenesis. Ischemia-reperfusion physiology is a key component of the inflammatory and vaso-occlusive milieu in SCD and is associated with complement activation. C5a is an anaphylatoxin, a potent pro-inflammatory mediator that can activate leukocytes, platelets, and endothelial cells, all of which play a role in vaso-occlusion. We hypothesize that hypoxia-reoxygenation (H/R) in SCD mice activates complement, promoting inflammation and vaso-occlusion. At baseline and after H/R, sickle Townes-SS mice had increased C3 activation fragments and C5b-9 deposition in kidneys, livers and lungs and alternative pathway Bb fragments in plasma compared to control AA-mice. Activated complement promoted vaso-occlusion (microvascular stasis) in SS-mice; infusion of zymosan-activated, but not heat-inactivated serum, induced substantial vaso-occlusion in the skin venules of SS-mice. Infusion of recombinant C5a induced stasis in SS, but not AA-mice that was blocked by anti-C5a receptor (C5aR) IgG. C5a-mediated stasis was accompanied by inflammatory responses in SS-mice including NF-κB activation and increased expression of TLR4 and adhesion molecules VCAM-1, ICAM-1, and E-selectin in the liver. Anti-C5aR IgG blocked these inflammatory responses. Also, C5a rapidly up-regulated Weibel-Palade body P-selectin and von Willebrand factor on the surface of human umbilical vein endothelial cells in vitro and on vascular endothelium in vivo. In SS-mice, a blocking antibody to P-selectin inhibited C5a-induced stasis. Similarly, an antibody to C5 that blocks murine C5 cleavage or an antibody that blocks C5aR inhibited H/R-induced stasis in SS-mice. These results suggest that inhibition of C5a may be beneficial in SCD.

Differential gene expression analysis of sickle cell anemia in steady and crisis state

Sickle cell anemia is one of the most prevalent genetic diseases worldwide, showing great clinical heterogeneity. This study compared the gene expression patterns between sickle cell anemia pediatric patients in steady state and in crisis state, as compared to age-paired, healthy individuals. RNA sequencing was performed from these groups of patients/controls using Illumina HiSeq 2500 equipment. The resulting differentially expressed genes were loaded into QIAGEN's ingenuity pathway analysis. The results showed that EIF2 pathway and NRF2-mediated oxidative stress-response pathways were more highly activated both in steady state and in crisis patients, as compared to healthy individuals. In addition, we found increased activation of eIF4 and p70S6K signaling pathways in crisis state compared to healthy individuals. The transcription factor GATA-1 was found exclusively in steady state while SPI was found exclusively in crisis state. IL6 and VEGFA were found only in crisis state, while IL-1B was found exclusively in steady state. The regulator effects analysis revealed IgG1 as an upstream regulator in steady state compared to healthy individuals, resulting in invasion of prostate cancer cell lines as the disease/function outcome. For crisis-state patients versus healthy individuals, two networks of regulator effects revealed STAT1, CD40LG, TGM2, IRF7, IRF4, and IRF1 acting as upstream regulators, resulting in disease/function outcomes, including engulfment of cells and aggregation of blood cells and inflammation of joints. Our results indicated genes and pathways that can provide clues on the molecular events involved in the severity of sickle cell disease.

Ventricular global longitudinal strain is altered in children with sickle cell disease

Cardiac disease is the primary cause of death in sickle cell disease (SCD). Right and left ventricular global longitudinal strain (RVGLS, LVGLS) are early markers of systolic dysfunction but are not well investigated among children with SCD. One hundred and forty-three patients with HbSS or HbSβ⁰ -thalassaemia (median age 11 years, range 5-19 years) and 71 controls matched for age and sex were compared. RVGLS and LVGLS were measured and compared with conventional measures of echocardiography and markers of haemolysis and inflammation. RVGLS was higher in children with SCD than in controls (-25·72% ± 3·45% vs. -24·54% ± 2·41%, P = 0·005); LVGLS was not different. RVGLS decreased with older age in children with SCD (ρ = 0·338, P < 0·001) but not among controls. Decreased RVGLS was associated with increased left atrial end diastolic volume (ρ = 0·181, P = 0·04); RVGLS increased with cardiac output (r = -0·279, P = 0·01). RVGLS and LVGLS were not associated with disease-modifying therapies, degree of anaemia or haemolysis markers. Elevated RVGLS may indicate an early RV compensatory mechanism in response to upstream myocardial insults and elevated cardiac output. Global longitudinal strain may serve as an early marker of altered myocardial function in children with SCD.

A common molecular signature of patients with sickle cell disease revealed by microarray meta-analysis and a genome-wide association study

A chronic inflammatory state to a large extent explains sickle cell disease (SCD) pathophysiology. Nonetheless, the principal dysregulated factors affecting this major pathway and their mechanisms of action still have to be fully identified and elucidated. Integrating gene expression and genome-wide association study (GWAS) data analysis represents a novel approach to refining the identification of key mediators and functions in complex diseases. Here, we performed gene expression meta-analysis of five independent publicly available microarray datasets related to homozygous SS patients with SCD to identify a consensus SCD transcriptomic profile. The meta-analysis conducted using the MetaDE R package based on combining p values (maxP approach) identified 335 differentially expressed genes (DEGs; 224 upregulated and 111 downregulated). Functional gene set enrichment revealed the importance of several metabolic pathways, of innate immune responses, erythrocyte development, and hemostasis pathways. Advanced analyses of GWAS data generated within the framework of this study by means of the atSNP R package and SIFT tool identified 60 regulatory single-nucleotide polymorphisms (rSNPs) occurring in the promoter of 20 DEGs and a deleterious SNP, affecting CAMKK2 protein function. This novel database of candidate genes, transcription factors, and rSNPs associated with SCD provides new markers that may help to identify new therapeutic targets.

Inflammation in sickle cell disease

The primary β-globin gene mutation that causes sickle cell disease (SCD) has significant pathophysiological consequences that result in hemolytic events and the induction of the inflammatory processes that ultimately lead to vaso-occlusion. In addition to their role in the initiation of the acute painful vaso-occlusive episodes that are characteristic of SCD, inflammatory processes are also key components of many of the complications of the disease including autosplenectomy, acute chest syndrome, pulmonary hypertension, leg ulcers, nephropathy and stroke. We, herein, discuss the events that trigger inflammation in the disease, as well as the mechanisms, inflammatory molecules and cells that propagate these inflammatory processes. Given the central role that inflammation plays in SCD pathophysiology, many of the therapeutic approaches currently under pre-clinical and clinical development for the treatment of SCD endeavor to counter aspects or specific molecules of these inflammatory processes and it is possible that, in the future, we will see anti-inflammatory drugs being used either together with, or in place of, hydroxyurea in those SCD patients for whom hematopoietic stem cell transplants and evolving gene therapies are not a viable option.

Oxidative stress in sickle cell disease; more than a DAMP squib

Sickle cell disease (SCD) is a monogenetic disorder marked by hemolytic anemia and vaso-occlusive complications. The hallmark of SCD is the intracellular polymerization of sickle hemoglobin (HbS) after deoxygenation, and the subsequent characteristic shape change (sickling) of red cells. Vaso-occlusion occurs after endothelial activation, expression of adhesion molecules and subsequent adhesion of leucocytes and sickle erythrocytes to the vascular wall. Here we review how oxidative stress from various sources influences this process. Emerging evidence points towards a dominant mechanism in which innate immune receptors, such as Toll like receptor 4, activate nicotinamide adenine dinucleotide phosphate (NADPH) oxidases to produce reactive oxygen species (ROS) which in turn enables downstream pro-inflammatory signaling and subsequent endothelial activation. By serving as an iron donor for the Fenton reaction, heme radically increases the amount of ROS further, thereby increasing the signal originating from the innate immune receptor and downstream effects of innate immune receptor activation. In SCD this results in the production of pro-inflammatory cytokines, endothelial activation and leucocyte adhesion, and eventually vaso-occlusion. Any intervention to stop this cascade, including Toll like receptor blockade, NADPH oxidase inhibition, ROS reduction, heme scavenging, iron chelation, or anti-adhesion molecule antibodies has been successfully used in pre-clinical studies and holds promise for patients with SCD.

Induction of NLRP3 Inflammasome Activation by Heme in Human Endothelial Cells

Hemolytic or hemorrhagic episodes are often associated with inflammation even when infectious agents are absent suggesting that red blood cells (RBCs) release damage-associated molecular patterns (DAMPs). DAMPs activate immune and nonimmune cells through pattern recognition receptors. Heme, released from RBCs, is a DAMP and induces IL-1β production through the activation of the nucleotide-binding domain and leucine-rich repeat-containing family and pyrin domain containing 3 (NLRP3) in macrophages; however, other cellular targets of heme-mediated inflammasome activation were not investigated. Because of their location, endothelial cells can be largely exposed to RBC-derived DAMPs; therefore, we investigated whether heme and other hemoglobin- (Hb-) derived species induce NLRP3 inflammasome activation in these cells. We found that heme upregulated NLRP3 expression and induced active IL-1β production in human umbilical vein endothelial cells (HUVECs). LPS priming largely amplified the heme-mediated production of IL-1β. Heme administration into C57BL/6 mice induced caspase-1 activation and cleavage of IL-1β which was not observed in NLRP3^-/- mice. Unfettered production of reactive oxygen species played a critical role in heme-mediated NLRP3 activation. Activation of NLRP3 by heme required structural integrity of the heme molecule, as neither protoporphyrin IX nor iron-induced IL-1β production. Neither naive nor oxidized forms of Hb were able to induce IL-1β production in HUVECs. Our results identified endothelial cells as a target of heme-mediated NLRP3 activation that can contribute to the inflammation triggered by sterile hemolysis. Thus, understanding the characteristics and cellular counterparts of RBC-derived DAMPs might allow us to identify new therapeutic targets for hemolytic diseases.

Sickle cell disease

Sickle cell disease (SCD) is a group of inherited disorders caused by mutations in HBB, which encodes haemoglobin subunit β. The incidence is estimated to be between 300,000 and 400,000 neonates globally each year, the majority in sub-Saharan Africa. Haemoglobin molecules that include mutant sickle β-globin subunits can polymerize; erythrocytes that contain mostly haemoglobin polymers assume a sickled form and are prone to haemolysis. Other pathophysiological mechanisms that contribute to the SCD phenotype are vaso-occlusion and activation of the immune system. SCD is characterized by a remarkable phenotypic complexity. Common acute complications are acute pain events, acute chest syndrome and stroke; chronic complications (including chronic kidney disease) can damage all organs. Hydroxycarbamide, blood transfusions and haematopoietic stem cell transplantation can reduce the severity of the disease. Early diagnosis is crucial to improve survival, and universal newborn screening programmes have been implemented in some countries but are challenging in low-income, high-burden settings.

A genetic variant of NLRP1 gene is associated with asbestos body burden in patients with malignant pleural mesothelioma

The presence of asbestos bodies (ABs) in lung parenchyma is considered a histopathologic hallmark of past exposure to asbestos fibers, of which there was a population of longer fibers. The mechanisms underlying AB formation are complex, involving inflammatory responses and iron (Fe) metabolism. Thus, the responsiveness to AB formation is variable, with some individuals appearing to be poor AB formers. The aim of this study was to disclose the possible role of genetic variants of genes encoding inflammasome and iron metabolism proteins in the ability to form ABs in a population of 81 individuals from North East Italy, who died after having developed malignant pleural mesothelioma (MPM). This study included 86 genetic variants distributed in 10 genes involved in Fe metabolism and 7 genetic variants in two genes encoding for inflammasome molecules. Genotypes/haplotypes were compared according to the number of lung ABs. Data showed that the NLRP1 rs12150220 missense variant (H155L) was significantly correlated with numbers of ABs in MPM patients. Specifically, a low number of ABs was detected in individuals carrying the NLRP1 rs12150220 A/T genotype. Our findings suggest that the NLRP1 inflammasome might contribute in the development of lung ABs. It is postulated that the NLRP1 missense variant may be considered as one of the possible host genetic factors contributing to individual variability in coating efficiency, which needs to be taken when assessing occupational exposure to asbestos.

Heme-mediated cell activation: the inflammatory puzzle of sickle cell anemia

INTRODUCTION

Hemolysis triggers the onset of several clinical manifestations of sickle cell anemia (SCA). During hemolysis, heme, which is derived from hemoglobin (Hb), accumulates due to the inability of detoxification systems to scavenge sufficiently. Heme exerts multiple harmful effects, including leukocyte activation and migration, enhanced adhesion molecule expression by endothelial cells and the production of pro-oxidant molecules. Area covered: In this review, we describe the effects of heme on leukocytes and endothelial cells, as well as the features of vascular endothelial cells related to vaso-occlusion in SCA. Expert commentary: Free Hb, heme and iron, potent cytotoxic intravascular molecules released during hemolysis, can exacerbate, modulate and maintain the inflammatory response, a main feature of SCA. Endothelial cells in the vascular environment, as well as leukocytes, can become activated via the molecular signaling effects of heme. Due to the hemolytic nature of SCA, hemolysis represents an interesting therapeutic target for heme-scavenging purposes.